In many types of x-ray processes, it is necessary to provide on the x-ray film an indication of the location of the images that appear on the film. For example, it is common practice to inject dye into the bloodstream to locate arterial blockage. The dye is visible on the x-ray film and indicates the location of the blockage. Surgical or other techniques are then used to alleviate the blockage. In order to assure that incisions and other surgical procedures are carried out at the correct location, it is necessary for the location of the blockage on the x-ray film to be correlated with the body part in which the blockage occurs.
In the past, the common practice has been to place a ruler or other measuring stick with graduation marks that are opaque to x-rays against the body and then take the x-rays. The graduation marks are visible on the exposed x-ray film and indicate the location of the blockage or other problem.
One problem with this technique is that it is often inaccurate because the ruler or other measuring stick can move on the patient between the time of the x-rays and the time of the treatment. The ruler must also be sterilized prior to each use, and this takes the valuable time of hospital technicians or other personnel. The sterilization may be done improperly or incompletely, and this can create significant problems. At best, the use of a ruler is a problematical solution and at worst it is inaccurate and possibly even dangerous. The devices that have been used in the past are useful in only one place. Because accurate location usually requires views in two different planes, two different devices must be used if radiographs in two planes are required.